1. Field of the Invention
The present invention relates to an ink jet printer.
2. Description of Related Art
With a conventional color printer, colored ink is supplied from a corresponding ink tank to a corresponding printhead. Then, the colored ink is ejected through the orifices of the printhead in accordance with print data.
FIG. 10 is a perspective view of a relevant portion of a conventional ink jet printer. Referring to FIG. 10, a carriage 12 is slidably supported on a carriage shaft 11 and reciprocated along the carriage shaft 11. The carriage 12 carries four printheads 14 and an ink tank unit 15 thereon. The ink tank unit 15 includes four ink tanks 15Y, 15M, 15C, and 15B aligned in line from left to right in FIG. 10. The ink tanks 15Y, 15M, 15C, and 15B hold yellow ink, magenta ink, cyan ink, and black ink, respectively.
The ink tanks 15Y, 15M, 15C and 15B have ink exits 17Y, 17M, 17C, and 17B projecting downwardly from the bottom of the tanks. The carriage 12 has ink entrances 16Y, 16M, 16C, and 16B into which the ink exits 17Y, 17M, 17C, and 17B are fitted when the ink tanks are attached to the carriage 12.
The respective colored inks are directed via the ink entrances 16Y, 16M, 16C, 16B to the corresponding printheads 14 and are ejected through orifices, not shown. The ink tanks 15Y, 15M, 15C, and 15B are formed with recesses 15a in their side surfaces and the carriage 12 has upward projections 12m with latches 12h formed correspondingly to the recesses 15a. When the ink tank 15Y, 15M, 15C, and 15B are inserted into the carriage 12, the latches 12h will snap into the recesses 15a, holding the ink tank unit 15 in place.
In color printers, black ink is consumed more than inks of primary colors. Thus, the ink tanks 15Y, 15M, 15C and 15B are, for example, of the same height and depth but the ink tanks 15Y, 15M, and 15C are narrower in width than the ink tank 15B. Thus, the ink tank 15B has a larger volume than the other ink tanks, establishing a large volume ratio of the black ink to the ink tanks of primary color.
However, the ink tanks have ink exits formed at their bottom surfaces and therefore the width of the ink tanks cannot be smaller than the size of the ink exists. This indicates that the volume ratio of the ink tank of black to each of the ink tanks of primary colors cannot be increased any further for the same size of the carriage. This is a barrier to further miniaturization of the ink tanks.
One way of increasing the volume ratio is to make the ink tank 15B larger in the direction of the carriage shaft and to make the carriage larger in the direction of the carriage shaft accordingly. However, making the carriage larger in the direction of the carriage shaft is detrimental since such an increase in dimension increases the lateral dimension of the printer. The maximum width of a print medium that a printer can print is one of the major performances of the printer and it is desirable that a small-size printer can print on a print medium having a large width. Thus, increasing the lateral dimension of the printer is an obstacle to miniaturizing the printer.